1870

Soil Science

Vasily Dokuchaev (1846–1903)

Soils are the fine-grained physical and chemical weathering products of rocks exposed to Earth’s surface conditions. Wind, water, ice, tectonics, volcanic explosions, and even impact cratering are some of the agents that can break down or alter bedrock into soil. And as every farmer knows, soil is the critical carrier of nutrients and the storage medium for water that makes plant growth possible. Without soils, plants would struggle to survive, large-scale agriculture would be essentially impossible, and life on Earth would be dramatically different.

The study of soils as a distinct research area only began formally around 1870, spurred on by the Russian geologist Vasily Dokuchaev, who established many of the foundational principles upon which modern soil science is based. For example, Dokuchaev is credited with introducing the idea that variations in soils are correlated with variations in their starting bedrock composition, local climate conditions, local topography and drainage conditions, nature and influence of organisms that soils host and support, and the amount of time that soil formation processes have operated. He conducted extensive field studies of soils and developed one of the earliest soil classification systems (based on grain size, color, organic content, and other factors), some aspects of which are still used to classify soils today.

The study of the formation, chemistry, morphology, and classification of soils is known as pedology, and it encompasses a diverse range of academic and social disciplines, including geology, chemistry, mineralogy, ecology, microbiology, agronomy, archaeology, engineering, and even city and regional planning. In both academic and commercial realms, soil is rightly treated as a natural resource that, like other resources, deserves careful monitoring and proper management.

Because microscopic and macroscopic organisms play such an important role in the formation and modification of soils on Earth, it may be fair to ask, then: Are there soils on other moons or planets? Recently, the Soil Science Society of America decided that the answer is yes, changing their formal definition of “soil” to potentially include soils on other worlds by defining it as “the layer(s) of generally loose mineral and/or organic material that are affected by physical, chemical, and/or biological processes at or near a planet’s surface, and that usually hold liquids, gases, and biota, and support plants.”

Soils come in a variety of colors, textures, and compositions, as seen in this representative cross-section of soils beneath an asphalt road.